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Growing research has proposed that rheumatoid arthritis (RA) and chronic periodontitis (CP) share similar pathophysiological mechanisms involving inflammation and tissue destruction. However, the potential correlation of CP as a contributing factor for the occurrence of RA warrants validation in the Korean population, where both diseases are prevalent, especially considering the increasingly aging demographic in Korea. This study examined 5139 RA cases and 509,727 matched controls from a Korean national cohort dataset (2002–2019) by carefully employing propensity score matching to ensure comparability between groups. Baseline characteristics were compared using standardized differences, and logistic regression was employed to estimate the impact of CP history on RA likelihood while controlling for covariates. We fully examined medical records documenting CP occurrences within the two-year period leading up to the index date, conducting comprehensive subgroup analyses. While a 1-year history of CP did not show a significant association with likelihood of RA, a 2-year history of CP increased RA likelihood by 12%, particularly among older adults, females, rural residents, and those with certain comorbidities such as hypercholesterolemia. Interestingly, this association persisted even among individuals with non-smoking habits, normal weight, and infrequent alcohol consumption. These findings suggest that chronic CP exposure for at least 2 years may independently elevate RA risk in Korean adults. The association in certain subgroups appears to suggest a predisposition toward genetic susceptibilities over lifestyle and environmental factors. Predicting RA in CP patients may be challenging, emphasizing the importance of regular RA screening, especially in high-risk subgroups. [ABSTRACT FROM AUTHOR]

Given the global significance of gout and gastric cancer (GC) as major health problems with interrelated impacts, we examined the development of GC in Korean patients with gout. We conducted a nested case–control study using data from 10,174 GC patients and 40,696 control patients from the Korean National Health Insurance Service-National Sample Cohort database. Propensity score matching (1:4) with propensity score overlap-weighted adjustment was used to reduce selection bias and estimate the odds ratio (OR) and 95% confidence intervals (CIs) for the association between gout and GC. An adjusted OR for GC was not significantly higher in patients with gout than in control patients (1.02; 95% CI, 0.93–1.12; p = 0.652). Additionally, no association between gout and GC was observed in subgroup analyses such as sex, age, level of income, region of residence, or Charlson Comorbidity Index score. In conclusion, these results suggest that gout is not a significant independent risk factor for GC among the Korean population. Additional investigation is required to establish a causal association between gout and GC, and to generalize these results to general populations. [ABSTRACT FROM AUTHOR]

This study aimed to investigate the changes in physical activity levels and the rate of falls during the COVID-19 pandemic in the Korean population. The Korean Community Health Survey (KCHS) conducted in 2019 was compared with that conducted in 2020. Simple or multiple linear regression with complex sampling was conducted to calculate the estimated value (EV) of physical activity in the 2020 group vs. the 2019 group. The odds ratio (OR) of fall histories was calculated using simple or multiple logistic regression with complex sampling for the 2020 group compared to the 2019 group. The time spent on vigorous and moderate physical activity was lower in the 2020 group than in the 2019 group (EV = −10.0, 95% CI = −12.1 to −8.0, P < 0.001 for vigorous exercise and EV = −24.0, 95% CI = −26.7 to −21.4, P < 0.001 for moderate exercise). The rate of falls was lower in the 2020 group than in the 2019 group (OR = 0.66, 95% CI = 0.62 to 0.70, P < 0.001). Vigorous and moderate exercise decreased after the COVID-19 pandemic compared to before the pandemic. The occurrence of falls was lower during the COVID-19 pandemic than in the pre-pandemic period. [ABSTRACT FROM AUTHOR]

Simple Summary: We conducted a study using the Korean National Health Insurance Service–National Sample Cohort database to investigate if a hazard connection existed between prior use of proton pump inhibitors (PPIs) and the development of colorectal cancer (CRC) in the Korean population. Our research, which employed a nested case–control study with a statistical technique known as "propensity score nested weighted multivariate logistic regression", revealed that the risk of developing CRC increased regardless of whether individuals had a history of PPI use or the duration of PPI use. This suggests that prior use of PPIs, whether currently or in the past, and regardless of the duration, may be linked to an increased likelihood of CRC within the Korean population, highlighting the need for cautious and precise adherence to PPI medications according to treatment guidelines to mitigate potential adverse effects. The potential connection between proton pump inhibitors (PPIs) and colorectal cancer (CRC) risk remains unclear, with specific ethnic genetic backgrounds playing a role in PPI-induced adverse effects. In this nested case–control study, we investigated the risk of CRC in relation to preceding PPI use and the duration of use using data from the Korean National Health Insurance Service–National Sample Cohort database, including 9374 incident CRC patients and 37,496 controls. To assess the impact of preceding PPI exposure (past vs. current) and use duration (days: <30, 30–90, and ≥90) on incident CRC, we conducted propensity score overlap-weighted multivariate logistic regression analyses, adjusted for confounding factors. Our findings revealed that past and current PPI users had an increased likelihood of developing CRC. Regardless of duration, individuals who used PPIs also had higher odds of developing CRC. Subgroup analyses revealed that CRC occurrence increased independent of history or duration of prior PPI use, consistent across various factors such as age, sex, income level, and residential area. These findings suggest that PPI use, regardless of past or present use and duration of use, may be related to an increased risk of developing CRC in the Korean population. [ABSTRACT FROM AUTHOR]

Simple Summary: Using Korean National Health Insurance Service-National Sample Cohort database, we studied whether patient-specific factors such as age, gender, socioeconomic status, and presence of comorbidities may influence the relationship between gout and the likelihood of developing CRC. Our nested case-control study with propensity score overlap-weighted multivariate logistic regression analyses suggest that patients with gout are not at higher risk for CRC than a control group, indicating that gout may not significantly and independently contribute to the CRC risk of the general population. Nevertheless, within a specific subgroup of patients aged less than 65 years, there appeared to be a moderately reduced probability of CRC development. Further comprehensive research is necessary to substantiate this association and gain a better understanding of the underlying causal factors. Considering the global importance of both gout and colorectal cancer (CRC) as significant health issues with mutual relevance, we aimed to examine the risk of colorectal cancer in Korean patients with gout. In this nested case-control study, we used data from 9920 CRC patients and 39,680 controls the Korean National Health Insurance Service-National Sample Cohort database. Propensity score overlap-weighted multivariate logistic regression analyses, adjusted for confounders, were used to assess the odds ratio (OR) and 95% confidence interval (CI) of the association between gout and CRC. Adjusted OR for CRC were similar between patients with gout and the control group (0.95; 95% CI, 0.86–1.04; p = 0.282). However, after adjustment, subgroup analysis revealed an 18% reduction in the probability of CRC among patients younger than 65 years with gout (95% CI, 0.70–0.95; p = 0.009). Conversely, absence of an association between gout and subsequent CRC persisted regardless of sex, income, residence, and Charlson Comorbidity Index score, even among individuals aged 65 years or older. These results imply that gout may not be a significant independent risk factor for CRC among the general population. However, in patients younger than 65 years with gout, a slightly reduced likelihood of CRC was observed. Further research is necessary to establish a causal relationship between gout and CRC and to generalize these findings to other populations. [ABSTRACT FROM AUTHOR]

Simple Summary: This research investigates the potential link between gum disease and stomach cancer in the Korean population. In this study, we analyzed data from over 10,000 people with gastric cancer and 40,000 healthy individuals. The results indicate that individuals who had gum disease in the past one to two years were more likely to develop stomach cancer. This association was consistently observed in different groups, such as men under 65 years old. The study emphasizes the importance of regular screening for stomach cancer, particularly for those at high risk, such as individuals with a history of gum disease. These findings contribute to our understanding of the connection between oral health and stomach cancer and may guide future preventive measures. There is limited information regarding the potential association between chronic periodontitis (CP) and gastric cancer, especially in the Korean population. This study aimed to explore this relationship. This nested case–control study analyzed data from 10,174 patients with gastric cancer and 40,696 controls from the Korean National Health Insurance Service–National Sample Cohort using propensity score matching. Standardized differences were used to compare baseline characteristics between study groups. Logistic regression analyses adjusted for confounders were conducted to assess the association between history of CP and gastric cancer occurrence. CP histories and comprehensive subgroup analyses in the 1- and 2-year periods preceding the index date were evaluated. Individuals with a history of CP within the 1-year and 2-year periods showed an increased likelihood of developing gastric cancer. Subgroup analyses consistently supported these findings in male participants aged <65 years and individuals with various income levels or living in residential areas. However, no significant associations were observed among participants aged ≥65 years. In conclusion, CP may be a potential risk factor for gastric cancer development in the Korean population. Regular screening for gastric cancer may be necessary for high-risk individuals, specifically men aged <65 years with a history of CP. [ABSTRACT FROM AUTHOR]

A connection between asthma and the occurrence of Parkinson's disease (PD) has been suggested, but the findings have been contentious and require verification. In this nested case–control study using data from the Korean National Health Insurance Service—Health Screening Cohort (2002–2019), which comprised 9029 participants with PD and 36,116 matched controls, we explored the relationship between asthma and incident PD. An overlap-weighted logistic regression model was used to measure the probability of asthma and PD. After adjusting for various covariates, we found that asthma was related to a 1.11-fold greater probability of PD (95% confidence interval: 1.06–1.16). A subgroup analysis showed that this effect was independent of age, sex, residential area, or alcohol consumption, and that it was still noticeable even among patients with a high income; those with a normal weight or obesity; those who were non-smokers or current smokers; and those with no history of chronic obstructive pulmonary disease, hypertension, hyperglycemia, hyperlipidemia, or anemia. Thus, these findings may indicate that asthma may slightly augment the likelihood of PD in the Korean adult population regardless of demographic or lifestyle factors, making it difficult to predict PD in asthma patients. [ABSTRACT FROM AUTHOR]

A few retrospective studies have suggested the risk of urolithiasis associated with the use of proton pump inhibitors (PPIs). The current research intended to estimate the risk of urolithiasis according to previous PPI use. A nested case-control study was conducted using the National Health Insurance Service-National Health Screening Cohort in Korea. A total of 28,962 patients with urolithiasis and 115,848 control participants were selected. The previous prescription history of PPI with days of PPI prescription was collected. To calculate the odds ratios (OR) of past, current, and days of PPI use for urolithiasis, logistic regression models were used. Subgroup analyses were conducted. The urolithiasis group demonstrated a higher rate of current PPI users than the control group (60.9% vs. 43.7%). The current PPI users indicated 2.49 times higher odds for urolithiasis than no PPI users (95% confidence intervals [CI] = 2.33–2.66). A longer duration of PPI use was associated with greater odds for urolithiasis (adjusted OR = 1.65 (95% CI = 1.54–1.77) < 1.97 (95% CI = 1.84–2.11) < 2.32 (95% CI = 2.14–2.49) for 1–19 days, 30–364 days, and 365 or more days of PPI prescription). All subgroup analyses described a consistently positive association of previous PPI use with urolithiasis. Prior PPI use was related to a higher risk of urolithiasis. The relationship between previous PPI use and urolithiasis demonstrated a dose-response association. [ABSTRACT FROM AUTHOR]

Background: Safety concerns against the use of proton pump inhibitors (PPIs) based on the risk of dementia, especially Alzheimer's disease (AD), remain controversial. Here, we investigated the likelihood of AD depending on previous PPI exposure, use duration, and PPI generation. Methods: This nested case–control study comprised 17,225 AD patients who were 1:4 matched with 68,900 controls for age, sex, income, and region of residence from Korean National Health Insurance Service-Health Screening Cohort data between 2002 and 2015 using propensity-score matching method. Conditional and unconditional logistic regression analyses were used to evaluate the effects of previous PPI use on AD adjusting for multiple covariates. Results: Prior PPI use increased likelihood for AD in current and past PPI users (adjusted odds ratio 1.36 [95% confidence interval (CI) = 1.26–1.46] and 1.11 [95% CI = 1.04–1.18], respectively). Participants with either < 30 days, 30–90 days, or > 90 days of PPI prescription showed higher odds for AD (1.13 [95% CI = 1.07–1.19]; 1.18 [95% CI = 1.10–1.27]; 1.26 [95% CI = 1.16–1.36], respectively). Participants with either 1st-generation or 2nd-generation PPIs demonstrated higher incidences of AD in those with < 30 days (1.14 [95% CI = 1.07–1.22] and 1.13 [95% CI = 1.05–1.22], respectively), 30–90 days (1.19 [95% CI = 1.09–1.30] and 1.17 [95% CI = 1.05–1.29], respectively), or > 90 days (1.18 [95% CI = 1.07–1.30] and 1.27 [95% CI = 1.14–1.43], respectively) of prescription. Conclusions: Prior PPI use, regardless of current or past exposure, duration of use, or use of 1st- or 2nd-generation PPIs, may increase likelihood of AD, providing supportive evidence of previous pharmacoepidemiologic studies. [ABSTRACT FROM AUTHOR]

Background: Proton-pump inhibitors (PPIs) block acid secretion from gastric parietal cells; however, recent studies have reported that PPIs have antioxidant and anti-inflammatory properties in various cells. Newer PPIs are stronger inhibitors of acid secretion; however, the anti-inflammatory effects of these drugs have not been assessed. We evaluated anti-inflammatory effect of PPIs on the development of asthma/asthma exacerbation (AE) in a national health screening cohort. Methods: This case-control study comprised 64,809 participants with asthma who were 1:1 matched with controls from the Korean National Health Insurance Service-Health Screening Cohort. Conditional logistic regression analysis was used to evaluate the effect of previous PPI use on an asthma diagnosis in all participants. Unconditional logistic regression was used to assess the effect of PPI use on AE in participants with asthma. These relationships were estimated in a subgroup analysis according to PPI generation. Results: Overall, PPI use increased the risk of asthma diagnosis [adjusted odds ratio (aOR) = 1.29, 95% confidence interval (CI) = 1.23–1.35, p < 0.001]. Use of the first-generation PPIs was associated with asthma (aOR = 1.34, 95% CI = 1.18–1.52, p < 0.001), while use of second-generation PPIs was not (aOR = 0.97, 95% CI = 0.82–1.15, p = 0.748). In contrast, overall PPI use decreased the risk of AE in participants with asthma (aOR = 0.79, 95% CI = 0.75–0.84, p < 0.001), although this effect was observed only for second-generation PPIs (aOR = 0.76, 95% CI = 0.65–0.89, p = 0.001). Conclusion: PPI use increased the risk for subsequent asthma diagnosis. However, this effect was confined to first-generation PPIs. Second-generation PPIs decreased the risk of AE. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the relationship between chronic rhinosinusitis (CRS) and proton pump inhibitor (PPI) use in a Korean population. The Korea National Health Insurance Service-National Sample Cohort was assessed from 2002 to 2013. Patients with CRS (n = 7194) and control participants (n = 28,776) were matched by random order at a 1:4 ratio for age, sex, income group, region of residence, and index date. We analyzed PPI use by patients with and without CRS. ICD-10 codes defined CRS, and claim codes defined previous PPI use. Conditional logistic regression analyzed the crude and adjusted odds ratios (ORs) with 95% confidence intervals (CI). Subgroup analyses were performed according to age and sex. There was a difference in PPI prescription history and prescription duration between the CRS and control groups. The rate of CRS was higher in current (33.8% [263/778]) and past (26.3% [713/2708]) PPI users than PPI non-users (19.1% [6218/32,484], P < 0.001). The adjusted OR (aOR) of CRS with/without nasal polyps was 1.71 (95% CI 1.46–2.02, P < 0.001) and 1.28 (95% CI 1.16–1.41, P < 0.001) in current and past PPI users, respectively. Irrespective of PPI prescription days, PPI use was associated with higher CRS occurrence (aOR 1.46; 95% CI 1.26–1.69, P < 0.001) in the 30–89-day PPI user group. The subgroup analyses results were consistent. The ORs of CRS were higher in PPI users than in the controls, and consistently so in all age and sex groups. [ABSTRACT FROM AUTHOR]

In this study, we investigated the risk of thyroid cancer in patients with gout. Participants ≥40 years old in the Korean National Health Insurance Service–Health Screening Cohort were investigated. A total of 5844 patients with thyroid cancer were paired with 23,376 comparison participants (no history of thyroid cancer) to build the nested case–control study. A previous history of gout was collected from both the thyroid cancer and comparison participants. The relationship of thyroid cancer with a prior history of gout was analyzed using a conditional logistic regression model. The rate of gout was higher in the patients with thyroid cancer than in the comparison group. In the total study population, the relationship of thyroid cancer with a prior history of gout was not statistically evident. A previous history of gout was related to an increased risk of gout in the <60 years old, normal weight, abnormal blood pressure, and CCI score = 0 groups. The occurrence of thyroid cancer was not associated with a prior history of gout in the general adult population. However, a prior history of gout was related to an elevated risk of thyroid cancer in middle-aged and healthy populations without comorbidities. [ABSTRACT FROM AUTHOR]

Although safety concerns regarding proton pump inhibitor (PPI)/H2-receptor antagonists (H2RA) in the incident esophageal cancer have been raised, the Asian-based report is unclear. We investigated the estimated likelihood of incident esophageal cancer—its mortality depending on prior history of PPI/H2RA use—and gastroesophageal reflux disease (GERD) in Koreans. Using the Korean National Health Insurance Service-Health Screening Cohort data (2002–2015), a case–control study was retrospectively conducted, including 811 patients with incident esophageal cancer and 3244 controls matched with sex, age, income, and residence. Propensity score overlap weighting was adjusted to balance the baseline covariates. Overlap propensity score-weighted logistic regression analyses were assessed to determine associations of the prior exposure of PPI/H2RA (current vs. past) and the medication duration (<30-, 30–90-, vs. ≥90-days) with incident esophageal cancer and its mortality among the total participants or those with/without the GERD episodes, after adjusting for multiple covariates including PPI/H2RA. The current exposure to either PPI or H2RA showed higher odds for incident esophageal cancer than the nonuser group ([13.23; 95%CI 10.25–17.06] and [4.34; 95%CI 3.67–5.14], respectively), especially in all adults over the age of 40 years without GERD. Both current and past exposures to PPI showed a decreased probability of mortality compared with those of the nonuser group ([0.62; 95%CI 0.45–0.86] and [0.41; 95%CI 0.25–0.67], respectively). However, current or past exposure to H2RA harbored the mutually different likelihoods for mortality depending on the presence of GERD and old age. This study carefully speculates on the possible link between PPI/H2RA and incident esophageal cancer in the Korean population. Mortality appears to be affected by certain risk factors depending on drug types, exposure history, old age, and the presence of GERD. [ABSTRACT FROM AUTHOR]

The prevalence of neurodegenerative dementia is increasing owing to the rapid growth of the older population. We investigated risks and causes of mortality in Korean patients with neurodegenerative dementia using data from the Korean Health Insurance Review and Assessment Service-National Sample Cohort with the aim to improve their care. From a pool of 1,125,691 patients, 11,215 patients aged ≥60 years who were diagnosed with dementia between 2002 and 2013 were examined along with 44,860 matched controls. A Cox proportional hazard model was used to calculate crude and adjusted hazard ratios (HRs). During the follow-up period, 34.5% and 18.8% of individuals in the neurodegenerative dementia and control groups, respectively, died (P < 0.001). The adjusted HR for mortality in the neurodegenerative dementia group was 2.11 (2.41 and 1.96 in men and women, respectively). Moreover, the adjusted HRs in patients with neurodegenerative dementia were 3.25, 2.77, and 1.84 for those diagnosed at ages 60–69, 70–79, and ≥80 years, respectively. The highest odds ratio for mortality was noted among patients with neurologic disease (15.93) followed by those with mental disease (4.89). These data show that the risk of mortality increased regardless of age and sex in Korean patients with neurodegenerative dementia. [ABSTRACT FROM AUTHOR]

The objective of this study was to evaluate the influence of exposure to meteorological conditions, including air pollution, on thyroid cancer. A nested case–control study was conducted utilizing 4632 patients with thyroid cancer and 18,528 control subjects who were matched at a 1:4 ratio by age group, sex, income, and region of residence. Korean National Health Insurance Service-Health Screening Cohort data from 2002 to 2015 were used. Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated for thyroid cancer correlated with meteorological and air pollution exposure over a moving average of 3 years before the index dates. For all participants, the adjusted ORs associated with relative humidity (1.01, 95% CI 1.00–1.03, P value = 0.023), ambient atmospheric pressure (1.02, 95% CI 1.01–1.03, P value < 0.001), and sunshine duration (1.17, 95% CI 1.04–1.31, P value = 0.007) indicated correlations with the occurrence of thyroid cancer; however, these results were inconsistent in the subgroup analyses. Overall, exposure to nitrogen dioxide (NO2) (1.33, 95% CI 1.24–1.43, P value < 0.001) and particulate matter (PM10) (0.64, 95% CI 0.60–0.69, P value < 0.001) were related to thyroid cancer. These relationships persisted in the subgroup analyses. In conclusion, thyroid cancer occurrence was positively associated with NO2 exposure and negatively associated with PM10 exposure. [ABSTRACT FROM AUTHOR]

Background: Although the dopaminergic system is interconnected with the hypothalamic-pituitary-thyroid axis, few studies have explained the causal relationship between thyroid disease and Parkinson's disease (PD). Objective: The goal of this study was to investigate the association between thyroid diseases and PD in Korean residents. Methods: The Korean National Health Insurance Service-National Sample Cohort, which includes individuals aged ≥40 years, was assessed from 2002 to 2015. A total of 5,586 PD patients were matched by age, sex, income, and the region of residence with 22,344 control participants at a ratio of 1:4. In the PD and control groups, previous histories of levothyroxine treatment, goiter, hypothyroidism, thyroiditis, and hyperthyroidism were investigated. Results: The rates of levothyroxine treatment for more than 3 months, hypothyroidism, and hyperthyroidism were higher in the PD group than the control group (3.2%, 3.8%, and 2.8% vs. 2.5%, 2.9%, and 1.9%, respectively, p < 0.05). The adjusted odds ratios (ORs) in model 2, which was adjusted for all potential confounders, for hypothyroidism and hyperthyroidism in the PD group were 1.25 (95% confidence interval (CI) 1.01–1.55, p = 0.044) and 1.37 (95% CI 1.13–1.67, p = 0.002), respectively. In subgroup analyses, the association between hypothyroidism and PD was maintained in men older than 70 years and the association between hyperthyroidism and PD was maintained in women younger than 70 years. Conclusion: Both hyperthyroidism and hypothyroidism were associated with higher risk of PD, particularly for women younger than 70 years and men older than 70 years, respectively. [ABSTRACT FROM AUTHOR]

Background: Hepatitis B virus (HBV) and hepatitis C virus (HCV) are suspected of being associated with non‐Hodgkin lymphoma (NHL); however, persuasive data are lacking. Hence, a nested large‐population case‐control study was performed to investigate such associations in Koreans. Methods: Data were collected from 929 patients with NHL and 3716 healthy subjects, who were matched 1:4 for age, sex, income, and region of residence, from the Korean Health Insurance Review and Assessment Service‐National Sample Cohort. The diagnoses of NHL and HBV/HCV infection were based on the International Classification of Diseases (version 10) codes. Conditional logistic regression models were used to assess odds ratios (ORs) for NHL with respect to HBV or HCV with adjustment for the Charlson comorbidity index. Results: HBV and HCV rates were higher in the NHL group (3.3% and 1.3%, respectively) than in the control group (0.9% and 0.3%, respectively; P <.001 for each). The adjusted OR of hepatitis infection in patients with NHL were 3.25 (95% confidence interval [CI] = 1.99‐5.31) for HBV and 3.36 (95% CI = 1.51‐7.46) for HCV (P <.001 for each). Subgroups categorized by age (<55 vs ≥55 years) or sex showed significantly higher adjusted ORs of HBV for NHL. Moreover, patients with NHL ≥ 55 years of age or those who were female showed significantly higher adjusted ORs of HCV; those <55 years or who were male also tended to have higher ORs of HCV. Conclusion: Infection with either HBV or HCV is associated with NHL in Koreans. Highlights: The rates of HBV and HCV infections were higher in the NHL group than in the control group. Patients with NHL had higher odds ratios for HBV and HCV infections than control patients without NHL. [ABSTRACT FROM AUTHOR]

Background: This study aimed to complement previous studies on the risk of herpes zoster in the asthmatic adult population. Methods: The Korean Health Insurance Review and Assessment Service—National Sample Cohort (HIRA-NSC) from 2002 through 2013 was used. A total of 64,152 participants with herpes zoster were matched for age, sex, income, region of residence, hypertension, diabetes, and dyslipidemia with 239,780 participants who were included as a control group. In both the herpes zoster and control groups, previous history of asthma were investigated. The crude and adjusted odds ratios (ORs) and 95% confidence intervals (CI) of asthma for herpes zoster were analyzed using unconditional logistic regression analysis. Subgroup analyses were conducted according to age and sex. Results: Approximately 16.2% (9728/59,945) and 12.8% (30,752/239,780) of participants in the herpes zoster and control groups, respectively, had a previous history of asthma (P < 0.001). The herpes zoster group demonstrated a 1.32-times higher odds of asthma than the control group (95% CI 1.28–1.35, P < 0.001). The increased odds of asthma in the herpes zoster group persisted in all the age and sex subgroups. Conclusions: The odds for asthma were higher in the herpes zoster group. [ABSTRACT FROM AUTHOR]

Objectives: The present study evaluated the associations between rheumatoid arthritis (RA) and neurodegenerative dementia using a Korean national sample cohort. Methods: We designed two studies using the Korean National Health Insurance Service-National Sample Cohort from 2002 to 2013. Study I included participants with dementia matched 1:4 with controls and analyzed the participants' history of RA. Study II included participants with RA matched 1:4 with controls and analyzed the occurrence of dementia. RA was defined by the presence of relevant ICD-10 codes (M05 or M06) and medication histories. Neurodegenerative dementia was defined using ICD-10 codes (G30 or F00). Crude and adjusted odds ratios (ORs) were analyzed using conditional logistic regression analyses. Crude and adjusted hazard ratios (HRs) were analyzed using the stratified Cox proportional hazard model. Subgroup analyses were performed on groups stratified by age and sex. Results: The adjusted ORs for RA were 0.96 (95% CI = 0.78–1.16, P = 0.644) in the dementia group in study I. The adjusted HRs for dementia were 0.91 (95% CI = 0.76–1.10, P = 0.319) in the RA group in study II. No subgroup analysis reached the statistical significance level. Conclusion: We could not identify any significant relationship between RA and dementia. Key Points • Two studies were conducted to identify the relationship between rheumatoid arthritis and dementia using national cohort data. • Neither study showed any association between rheumatoid arthritis and dementia. [ABSTRACT FROM AUTHOR]

Background: The purpose of this study was to further clarify the relationship between chronic rhinosinusitis (CRS) and osteoporosis in a Korean population. Methods: The Korean National Health Insurance Service‒National Sample Cohort, with subjects ≥50 years old, was assessed for the time period 2002‐2013. In total, 68,459 osteoporosis participants were matched with 68,459 control participants at a ratio of 1:1 with respect to age, sex, income group, region of residence, hypertension, diabetes, and dyslipidemia. We analyzed previous histories of CRS with/without nasal polyp in the osteoporosis and control groups. CRS and osteoporosis were included using codes from the International Classification of Diseases―tenth edition and claim codes. Crude and adjusted odds ratios (ORs) were analyzed using conditional logistic regression analyses. The 95% confidence intervals (CIs) were then calculated. Subgroup analyses were performed according to age and sex. Results: The rate of CRS with/without nasal polyp was higher in the osteoporosis group (3.0% [2078 of 68,459]) compared with the control group (2.0% [1344 of 68,459]) (p < 0.001). The adjusted OR of CRS with/without nasal polyp was 1.47 (95% CI, 1.37‐1.58; p < 0.001) in the osteoporosis group. The results of the subgroup analyses were consistent. Conclusion: The ORs of CRS were increased in osteoporosis participants. This relation was consistent in all age and sex groups. [ABSTRACT FROM AUTHOR]

Objectives. Chronic inflammatory disease might affect osteoporosis; however, few studies have reported the association between herpes zoster and osteoporosis. The goal of this study was to estimate the association between herpes zoster and osteoporosis in Korean residents. Methods. The Korean National Health Insurance Service-National Sample Cohort, which includes individuals aged ≥ 50 years, was assessed from 2002 to 2013. In total, 68,492 osteoporosis participants were matched with 68,492 control participants at a ratio of 1:1 by age, sex, income, and region of residence. We assayed the prior histories of herpes zoster in the osteoporosis and control groups. The diagnoses of herpes zoster and osteoporosis were based on ICD-10 codes and claim codes. Crude and adjusted models of odds ratios (ORs) were explored using conditional logistic regression analyses, and the 95% confidence intervals (CIs) were computed. The participants were stratified according to age, sex, income, and region of residence. Subgroup analyses were performed to investigate the role of age and sex. Results. The rate of herpes zoster in the osteoporosis group (5.1% [3,487/68,492]) was higher than that in the control group (4.0% [2,738/68,492]). The adjusted OR of herpes zoster in the osteoporosis group was 1.17 (95% CI = 1.11-1.24). In the subgroup analyses, the adjusted OR was 1.34 (95% CI = 1.01-1.78) among males aged < 65 years, 1.20 (95% CI = 1.12-1.29) among females aged < 65 years, and 1.19 (95% CI = 1.04-1.36) among males aged ≥ 65 years. Conclusion. The ORs of herpes zoster were increased among the osteoporosis patients. This correlation was reliable in all subgroups by age and sex except group of women ≥ 65 years old. [ABSTRACT FROM AUTHOR]

Concerns about the hazards of statins on the development and mortality of stomach cancers remain controversial. Here, we investigated the likelihood of incident gastric cancers and related mortality depending on statin exposure, statin type, and the duration of use. This nested case–control-designed study was composed of 8798 patients who were diagnosed with gastric cancer and matched with 35,192 controls at a 1:4 ratio based on propensity scores of age, sex, residential area, and income from the Korean National Health Insurance Service—Health Screening Cohort database (2002–2015). Propensity score overlap weighting was adjusted to balance the baseline covariates. Overlap propensity score-weighted logistic regression analyses were assessed to determine associations of the prior use of statins (any statin, hydrophilic statins vs. lipophilic statins) with incident gastric cancer and its mortality depending on the medication duration (<180 days, 180–545 days, and >545 days) after adjusting for multiple covariates. After adjustment, the use of any statin, hydrophilic statins, or lipophilic statins showed significant associations with lower odds for incident stomach cancer when used for a short-term period (180–545 days) (OR = 0.88, 95% CI = 0.81–0.86, p = 0.002; OR = 0.78, 95% CI = 0.66–0.92, p = 0.004; and OR = 0.91, 95% CI = 0.84–0.99, p = 0.039, respectively) compared to the control group. Hydrophilic statin use for 180–545 days was associated with 53% lower overall mortality (OR = 0.47; 95% CI = 0.29–0.77). In subgroup analyses, beneficial effects on both cancer development and mortality persisted in patients ≥65 years old, patients with normal blood pressure, and patients with high fasting glucose levels. There were no such associations with long-term statin use (>545 days). Thus, the current nationwide cohort study suggests that prior short-term statin use may have anti-gastric cancer benefits in elderly patients with hyperglycemia. [ABSTRACT FROM AUTHOR]

Simple Summary: The association of thyroid dysfunction and thyroiditis with the risk of thyroid cancer is an important issue in clinical practice, and is controversial due to various confounders, including screening effects. In this large-sample, population-based, nationwide study, we demonstrated that the screening effect likely significantly contributed to the positive associations of thyroid dysfunction and thyroiditis with thyroid cancer. After adjustment for this confounder, thyroid cancer risk was positively associated with hypothyroidism and thyroiditis but negatively associated with hyperthyroidism and Graves' disease. Multiple subgroup analyses showed consistent results. Given these overestimated associations, we suggest that unnecessary and excessive concerns or screening tests for thyroid cancer could be reduced in patients with thyroid dysfunction or thyroiditis. We aimed to assess the relationships of functional thyroid disease and thyroiditis with subsequent thyroid cancer, which is controversial due to various confounders, and the effect of thyroid disease workup on this association. We used the cohort data from 2002 to 2015 (Study I, n = 28,330) and the entire data from 2002 to 2019 (Study II, n = 883,074) of the Korean National Health Insurance Service database, and performed logistic regression and subgroup analyses with various covariates. In Study I, hypothyroidism, thyroiditis, autoimmune thyroiditis, hyperthyroidism, and Graves' disease showed positive associations with thyroid cancer. In Study II, after adjustment for covariates including the number of thyroid function tests, the ORs for thyroid cancer were significantly reduced in all thyroid diseases. Hypothyroidism, thyroiditis, and autoimmune thyroiditis were positively associated (adjusted odds ratio, OR (95% confidence interval, CI) 1.28 (1.25–1.32), 1.36 (1.31–1.42), and 1.17 (1.11–1.24), respectively), whereas hyperthyroidism and Graves' disease were negatively associated with thyroid cancer (adjusted OR (95% CI) 0.80 (0.77–0.83) and 0.69 (0.65–0.74), respectively). Multiple subgroup analyses in both studies showed consistent results. In this large population-based, nationwide study, we confirmed that thyroid disease workup leads to overestimation of associations of thyroid dysfunction and thyroiditis with thyroid cancer risk. [ABSTRACT FROM AUTHOR]

Background: Reports on the possible risks for Alzheimer's disease (AD) have included tooth loss as a potential risk factor. However, there are few studies addressing the association between tooth loss and AD in a large sample of participants. Accordingly, the objective of the current study was to explore the association of tooth loss with the development of AD in Korean adults. Methods: This nested case–control study, which is an analysis utilizing the data of the Korean National Health Insurance Service Health Screening Cohort study, randomly selected AD and control participants among Korean residents aged ≥60 years. The association between the number of missing teeth and AD occurrence was examined using a logistic regression model. Participants' lifestyle factors (smoking and alcohol consumption) and various medical conditions and comorbidities were included as covariates. Results: The mean number of missing teeth was 2.94 in the AD group and 2.59 in the control group. After adjusting for covariates, tooth loss was significantly associated with AD, with an odds ratio (OR) (per 16 missing teeth) of 1.15 (95% confidence interval (CI) = 1.07–1.23, p < 0.001). Conclusions: Tooth loss remained consistently significantly associated with an increased risk of AD for both upper and lower tooth loss. A higher number of missing teeth was related to a higher probability of AD occurrence in an elderly Korean population. Efforts to manage tooth loss could be a possible approach to prevent AD. [ABSTRACT FROM AUTHOR]

A number of studies report the incidence of Alzheimer's disease (AD) in patients taking statins, but the results are inconsistent. (1) Background: The present study investigated the cross-sectional association between previous statin use and the risk of AD development in Korean residents. (2) Methods: We used the Korean National Health Insurance Service-National Sample Cohort; 17,172 AD patients were matched by age, gender, income, and region of residence with 68,688 control participants at a ratio of 1:4. We used a multiple conditional logistic regression model to analyse the association between the number of days of statin use and AD occurrence. Further analyses were performed to identify whether this association is maintained for different ages, genders, socioeconomic status groups, and covariates. (3) Results: The odds ratio, which was adjusted for potential confounders, for the days of statin use per year in the AD group compared to the control group was 0.95 (95% confidence interval = 0.92–0.98; p = 0.003). The number of days of statin use in the AD group was significantly smaller in the subgroups of non-smokers and individuals with normal weight, alcohol consumption less than once a week, total cholesterol level below 200 mg/dL, systolic blood pressure below 140, diastolic blood pressure below 90, and fasting blood glucose below 100 mg/dL. (4) Conclusions: Our results suggest that statin use prevents the occurrence of AD. The effects of statin use in preventing AD may be greater in individuals at relatively low risk. [ABSTRACT FROM AUTHOR]

Background: This study investigated relationship between multiple thyroid disorders and benign paroxysmal positional vertigo (BPPV), adjusting for levothyroxine medication. Methods: The Korean National Health Insurance Service-Health Screening Cohort data from 2002 to 2015 were used. A total of 19,071 patients with BPPV were matched with 76,284 participants of a control group in a ratio of 1:4 for age, sex, income, and region of residence. The previous histories of thyroid disorders such as goiter, hypothyroidism, thyroiditis, hyperthyroidism, and autoimmune thyroiditis were investigated in both the BPPV and control groups. The odds ratios (ORs) for BPPV in thyroid diseases were calculated using conditional logistic regression analyses. Results: The histories of goiter (5.5% vs. 4.1%), hypothyroidism (4.7% vs. 3.7%), thyroiditis (2.1% vs. 1.6%), and hyperthyroidism (3.1% vs. 2.5%) were higher in the BPPV group than in the control group (all p < 0.001). Goiter, hypothyroidism, thyroiditis, and hyperthyroidism were associated with BPPV (adjusted OR = 1.28 (95% CI = 1.17–1.39) for goiter, 1.23 (95% CI = 1.10–1.37) for hypothyroidism, 1.13 (95% CI = 1.02–1.26) for hyperthyroidism, each p < 0.05). Conclusions: BPPV was associated with thyroid disorders such as goiter, hypothyroidism, thyroiditis, and hyperthyroidism. [ABSTRACT FROM AUTHOR]

Pneumonia and chronic otitis media (COM) share a common pathophysiological mechanism in terms of respiratory infection and inflammation, but the epidemiologic association between the 2 diseases has not been investigated. We investigated the association between an event of COM and previous events of pneumonia in a national cohort. Data from the Korean National Health Insurance Service-Health Screening Cohort were collected from 2002 to 2015. A 1:4 stratified cohort matched for age, sex, income, and residence region composing the COM group (n=23,436) and a control group (n=93,744) was selected. The crude and adjusted odds ratios (ORs) of pneumonia occurring before the index date for COM were analyzed using a conditional logistic regression model. In addition, ORs of the number of diagnoses of pneumonia (≥5 times vs. <5 times) for COM were analyzed. The incidence of pneumonia (9.3%) was significantly higher (p<0.001) in the COM group than in the control group (7.2%). The ORs of pneumonia were significantly higher in the COM group than in the control group. Pneumonia (adjusted OR=1.31, 95% confidence interval [CI]=1.25–1.38, p<0.001) increased the ORs for COM in all ages and gender. Pneumonia being diagnosed ≥5 times before the index date showed higher ORs (adjusted OR=1.34, 95% CI=1.20–1.49, p<0.001) for COM than pneumonia being diagnosed <5 times. Our population-based nationwide cohort study indicates that diagnosis of pneumonia was significantly associated with an increased incidence of COM. [ABSTRACT FROM AUTHOR]

Background: The purpose of this study was to evaluate the relations between gastroesophageal reflux disease (GERD) and chronic rhinosinusitus (CRS) in a Korean population. Methods: Subjects from the Korean National Health Insurance Service‒National Sample Cohort, all ≥20 years old, were assessed from 2002 to 2013. In total, 23,489 CRS participants were matched with 93,956 controls at a ratio of 1:4 with respect to age, group, sex, income group, region of residence, hypertension, diabetes, and dyslipidemia. We analyzed previous history of GERD in the CRS and control groups. The CRS group included patients identified using International Classification of Diseases 10th edition (ICD‐10) codes (J32) who had treated their CRS ≥2 times and had undergone head and neck computed tomography (CT). The GERD group included patients identified using the ICD‐10 (K21) code who had treated their GERD ≥2 times and had taken a proton pump inhibitor (PPI) for ≥2 weeks. Crude and adjusted odds ratios (ORs) were analyzed using unconditional logistic regression analyses. The 95% confidence intervals (CIs) were calculated. Subgroup analyses were performed according to age and sex. Results: The rate of GERD was higher in the CRS group (17.1% [4020 of 23,489]) than in the control group (9.1% [8522 of 93,956]; p < 0.001). The adjusted OR of GERD was 2.04 (95% CI, 1.96‐2.13; p < 0.001) in the CRS group. The results of the subgroup analyses were consistent. Conclusion: The ORs of GERD were increased in CRS participants. This relationship was consistent in all age and sex groups. [ABSTRACT FROM AUTHOR]